P2ACC

Code

Generic P — Powertrain

Reductant Temperature Sensor B Circuit

Brand: Generic

Type: P — Powertrain

Views: UK: 12 EN: 24 RU: 18

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Page language: EN

Causes

Open or shorted sensor harness (broken wire, chafing, pinched cable)
Corroded, loose or contaminated connector / terminals
Failed reductant temperature sensor (thermistor or internal heater)
Poor or missing reference power or ground to the sensor
Short to battery voltage or ground in signal wire
Water/contaminant ingress into sensor or connector

Symptoms

Malfunction indicator lamp (MIL) or malfunction light illuminated
Stored P2ACC fault and related freeze-frame data
Aftertreatment/DEF dosing faults or reduced SCR performance
Possible reduced emission control functionality, regen inhibited or warning message
No obvious change in engine running in some cases (electrical fault only)

What to check

Retrieve trouble codes and freeze-frame data with a scan tool; check for related DEF/SCR codes
Visual inspection of sensor B wiring and connector for damage, corrosion, water intrusion or loose pins
Backprobe the sensor connector and monitor signal voltage and reference power with ignition on (engine off) using a multimeter/scan tool
Measure sensor resistance vs. expected spec (thermistor); compare against ambient temperature (if service data available)
Wiggle harness and connectors while monitoring live data to find intermittent faults
Check continuity/shorts to power and ground on the signal circuit

Signal parameters

Typical sensor type: NTC thermistor (resistance changes with temperature); some designs provide a 0.1–4.9 V signal to the controller. Values vary by manufacturer.
Common expected behavior (generic): signal voltage decreases/increases smoothly with temperature changes; no sudden jumps or open-circuit voltage near battery voltage or 0 V
Typical resistance range at ambient may be within approximately 1 kΩ to 50 kΩ depending on sensor design—consult the vehicle manufacturer service data for exact resistances vs. temperature
Reference circuit: usually a regulated reference (5 V or similar) and a ground—verify presence of reference voltage and good ground at the connector

Diagnostic algorithm

Connect a professional scan tool, read all codes and freeze-frame. Note any other DEF/SCR or temperature sensor codes.
Perform a visual inspection of harness and connector for sensor B: look for corrosion, pushed-out pins, broken wires, chafing, or contamination. Repair obvious damage.
With ignition ON (engine OFF) backprobe the connector: verify sensor reference voltage (if provided by controller), signal voltage, and ground continuity. Compare to expected ranges in service data.
Measure sensor resistance with the sensor disconnected. Compare resistance to expected value for ambient temperature per service manual. If resistance is open or shorted, replace sensor.
Check continuity of the signal and ground wires from the sensor connector to the controller. Check for short to battery voltage or ground.
Perform a wiggle test on the harness and connector while monitoring live data or DTC status to reveal intermittent faults. Repair any intermittent wiring issues.
If wiring and sensor check good, inspect the ECU/module input (if accessible) or perform module bench test according to manufacturer procedures. Replace controller only after exhausting harness/sensor checks.
After repairs, clear codes and perform a road or operational test to confirm the fault does not return and vehicle returns to normal after system self-checks.

Likely causes

Damaged or corroded connector at the reductant temperature sensor
Open or shorted signal/ground wire between sensor B and controller
Failed sensor element (thermistor) due to contamination or age
Intermittent harness connection caused by vibration or routing near moving parts

Fault status

⚠️ Status

Reductant (DEF/urea) temperature sensor B circuit fault detected — open/short/intermittent signal. Inspect sensor B, its connector and wiring; verify reference voltage and ground; replace component(s) per test results.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-2.0 hours